I. Field of the Invention
This invention relates generally to electrosurgical instruments, and more particularly to an electrosurgical instrument for cutting and coagulating when performing minimally invasive surgery via an endoscope and incorporating means for quickly and easily removing and replacing the electrode structure. As used herein, the term "endoscope" is intended to genericly cover and include more specific instruments, including, for example, laparoscopes, cystoscopes, arthroscopes, hysteroscopes and the like.
II. Discussion of the Prior Art
With the advent of improved equipment for viewing a surgical site internal to the body using optical fibers routed through small diameter tubes, such as endoscopes, improved surgical procedures have been devised in which microminiaturized instruments may be routed through cannulae or a working lumen in the endoscope itself for surgically removing or repairing diseased or damaged organs without the need for making large incisions to expose the area allowing the surgeon to view the surgical site. For example, it is now possible in many cases to remove a defective gallbladder without making a large incision through the abdominal wall. Instead, in a procedure called laparoscopic cholecystectomy, a series of tiny puncture wounds are made through the abdomen and a laparoscope, for viewing the internal surgical site, and other tubes for passing cutting and/or grasping instruments are inserted. By appropriately manipulating the instruments within their respective tubes, the gallbladder can be excised from surrounding tissue, emptied of its contents and then retracted back through the small tube. Using this laparoscopic procedure, a patient who might otherwise be hospitalized for a week or more and who may have to undergo a month of recuperation before returning to normal activities can leave the hospital the next day and return to work within only a few days.
The laparoscopic cholecystectomy procedure alluded to above is only one of a series of surgical procedures that have been made possible using endoscopes and the like. In applicant's copending application Ser. No. 07/516,740, now U.S. Pat. No. 5,071,419, filed Apr. 30, 1990, and entitled "PERCUTANEOUS LAPAROSCOPIC CHOLECYSTECTOMY INSTRUMENT", there is described an electrosurgical instrument especially designed for carrying out minimally invasive procedures, via an endoscope-type device. It comprises an elongated tube having a pair of spaced-apart hook-shaped electrodes permanently affixed to the distal end thereof and a hub or handle member affixed to its proximal end. Electrical conductors enter the handle and pass through the lumen of the elongated tube and are electrically connected to the hook-shaped electrodes. Means are also provided for allowing irrigation and aspiration of the surgical site.
During a given surgical procedure, it may become necessary to substitute different electrodes, either because the existing electrodes become fouled with charred tissue and blood rendering them ineffective for cutting or because electrodes of differing shape configuration may more readily be used than the existing ones to surmount a particular obstacle or to achieve a more desired cutting pattern.
Prior to the present invention, electrosurgical instruments for endoscopic procedures all have had monopolar or bipolar electrodes permanently affixed to the distal end of the instrument. Hence, in the event that the electrosurgical electrodes became fouled to the point where they cannot be wiped clean, it has been necessary to remove and discard the entire instrument, thus adding to the cost of the procedure.